Field of the Disclosure
The present invention relates to an accelerator reaction force control apparatus which controls a reaction force of an accelerator of a vehicle.
Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2007-76468 (hereinafter referred to as Patent Document 1) discloses a technique for calculating an optimum amount of operation (optimum amount of depression) of an accelerator on the basis of a driving environment in which a vehicle is being driven. The optimum amount of operation is an amount of operation at which an optimum specific fuel consumption can be obtained. According to this technique, the calculated optimum amount of operation is corrected in accordance with the condition of the road in front of the vehicle. When a driver depresses the accelerator and the amount of operation becomes close to the corrected optimum amount of operation, an operational reaction force of the accelerator is increased stepwise. According to Patent Document 1, the optimum amount of operation is corrected such that the optimum amount of operation is reduced when the road in front of the vehicle is sloping downward or curved.
In the case where the road in front of the vehicle is sloping downward, the speed of the vehicle generally increases and the following distance to another vehicle decreases. Therefore, there is a high possibility that a brake will be applied. In addition, in the case where the road in front of the vehicle is curved, there is also a high possibility that a brake will be applied to facilitate the control of the vehicle when the vehicle enters the curve. Thus, according to Patent Document 1, the optimum amount of operation is reduced in the case where there is a high possibility that a brake will be applied, as in the case where the road in front of the vehicle is sloping downward or curved. As a result, the vehicle speed is reduced and the vehicle is prevented from driving along the road in front of the vehicle at an excessively high speed. In addition, an increase in the specific fuel consumption may be suppressed.
According to the technique discussed in Patent Document 1, a threshold of an accelerator opening degree or an accelerator depressing speed is set such that the optimum specific fuel consumption may be obtained, and the reaction force of the accelerator is increased at the threshold. However, the accelerator is a main device operated by the driver to operate the vehicle in a way that the driver desires. Therefore, the operational feel of the accelerator and the influence thereof on the vehicle driving performance directly affect the overall feeling of the driver. For this reason, this type of reaction-force control apparatus which contributes to the reduction in fuel consumption cannot be put into practical use unless the reduction in fuel consumption can be achieved together with satisfactory feel of the accelerator and operability of the vehicle.
Various tests for putting the reaction-force control apparatus which contributes to the reduction in fuel consumption into practical use have been conducted. As a result of these tests, it was found that the driver feels an uncomfortable sensation if the reaction force is simply increased at the threshold of the accelerator opening degree or the depressing speed set from the viewpoint of reducing the fuel consumption as in Patent Document 1. More specifically, in this type of reaction-force control apparatus, the reaction force of the accelerator is suddenly increased while the driver is trying to accelerate the vehicle. Therefore, when, for example, a driving force required to accelerate the vehicle is relatively large, the vehicle cannot be accelerated as intended by the driver, and this makes the driver feel uncomfortable.